A 230-foot-tall Falcon 9 rocket propelled the car-size spacecraft into orbit at 6:51 p.m. EDT on Wednesday, April 18. It will take about 68 days' worth of maneuvers, including a flyby of the moon, for TESS to slip into an unprecedented orbit and begin its 24-month search for thousands of new worlds.

The Transiting Exoplanet Survey Satellite at Kennedy Space Center in Florida before launch.NASA

NASA previously detected thousands of exoplanets with the planet-hunting Kepler space telescope. Extrapolating the results to the rest of the Milky Way, researchers believe there could be about 10 planets in our galaxy for each one of the galaxy's roughly 200 billion stars.

"We learned from Kepler that there are more planets than stars in our sky, and now TESS will open our eyes to the variety of planets around some of the closest stars," Paul Hertz, the director of NASA's astrophysics division, said in a press release. "TESS will cast a wider net than ever before for enigmatic worlds."

What's more, Hertz said, NASA's next "great observatory," the $8.8-billion James Webb Space Telescope, will use TESS's data to zero in on and study the most exciting nearby rocky planets (as will future ground-based telescopes).

Why TESS is such an important planet-hunting mission

The Kepler spacecraft stared down stars to detect dips in brightness caused by planets passing in front of their home stars. It did this for 150,000 stars in a part of the night sky that's just 0.25% of the total area, yet 3,000 light-years deep.

Kepler has found about 50 rocky and Earth-size worlds, 10 of which may be habitable, plus more than 4,000 total planet candidates since its launch in 2009. A Google artificial intelligence algorithm has since sifted through the data and possibly detected even more.

Meanwhile, TESS will gaze at 200,000 stars over most of the sky within a relatively cozy 200-light-year range of Earth.

If Kepler was a long-range sniper rifle that found thousands of planets in a narrow section, that makes TESS a grenade that will find thousands more nearby.

"TESS will discover thousands of planets and is further specially designed to find a pool of small planets transiting small stars," a website for the project explains. Specifically, researchers promise — based on Kepler's census — to serve up 50 rocky, Earth-size worlds for scientists to scrutinize.

The telescope will do this by taking photos with four cameras that were custom-built to detect minor changes in a star's brightness.

Over two years, TESS will photograph a different sector of the sky every 27 days. In two patches of space, all of the sectors overlap — providing about a year's worth of transit observations.

Any discoveries TESS makes in these patches, called "continuous viewing zones," could prove vital to JWST, which would be the largest observatory ever launched into space.

Now scheduled to launch around May 2020, the next-generation observatory will rival the abilities of the Hubble Space Telescope.

JWST will take pictures in infrared light, which is invisible to human eyes yet perfect for studying planets through clouds of gas and dust in space that typically obscure distant worlds.

The ability to study the air supply of a distant Earth-size planet is even more possible with the Giant Magellan Telescope (GMT), one of the two largest ground-based observatories under construction today.

Slated to open for business in 2023, GMT is designed to resolve details four times finer than JWST. This could help astronomers study exoplanets in ways what they've been dreaming of since the first confirmed discovery of an alien solar system in 1992.

"As a planet passes in front of its star, a large telescope on the ground, like the GMT, can use spectra to search for the fingerprints of molecules in the planetary atmosphere," Patrick McCarthy, a leader of the project, said in a statement to Business Insider.